Reference Manual

PMAC PCI Lite Hardware Reference Manual
Software Setup 23
To set up a board to communicate as Card 1 to Card 15 on a multi-drop serial cable, first communicate
with the board as Card 0. Set I0 to specify the card number (software address) that the board will have on
the multi-drop cable. Also, set I1 to 2 to enable the serial software addressing. Store these values to the
non-volatile flash memory with the SAVE command. Then turn off power. If the board is to input its
clocks, remove any of the E40-E43 jumpers. Connect the multi-drop cable. Restore power to the system.
Option 16 Supplemental Battery-Backed Memory
If Option 16 supplemental battery-backed parameter memory is ordered, an extra bank of memory with
battery backup circuitry is provided. This option can be ordered only if the main memory is flash backed
(Option 4A, 5A, 5B, or 5C). This memory is for user parameter storage only. From PMAC programs, it
can be accessed with M-variables only (L-variables also in compiled PLCs). The on-line direct-memory
read and write commands can be used from the host computer as well.
With M-variable access, arrays can be created with indirect addressing techniques by pointing a second
M-variable to the definition of a first M-variable that points into this memory area. For example, with the
M-variable definitions:
M0->L:$A000 ; 1st long word of Opt. 16 RAM; floating point
M10->Y:$BC000,0,16 ; Low 16 bits of M0 def., with pointer address
The following code segment could load a sine table into the first 360 words of the Option 16 RAM:
P1=0
WHILE (P1<360)
M10=$A000+P1 ; Sets address that M0 points to
M0=SIN(P1) ; Puts value in register that M0 points to
P1=P1+1
ENDWHILE
Note:
This technique is not possible with L-variables in compiled PLCs. However, it is
possible with M-variables in compiled PLCs.
Physically, the Option 16 memory is a 16k x 24 bank of battery-backed static RAM. It maps into the
PMAC and PMAC2 at addresses $A000 to $BFFF, on both the X and Y data buses, an 8k x 48 block of
address space. Addresses Y:$BC00 to Y:$BFFF are double-mapped with the main flash-backed RAM for
the M-variable definitions, and should not be used for user parameter storage.
Any value written into the Option 16 memory will be retained automatically through a power-down or
reset; no SAVE operation is required. The power draw on the battery is low enough that typically battery
life will be limited only by the quoted 10-year life of the battery.